A gas turbine engine may be used to power various types of vehicles and systems. A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, five major sections, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. Each section includes components that are coupled to a rotor and disposed within an engine housing. The fan section is positioned at the front, or “inlet” section of the engine, and includes a fan that induces air from the surrounding environment into the engine, and accelerates a fraction of this air toward the compressor section. The remaining fraction of air induced into the fan section is accelerated into and through a bypass plenum, and out the exhaust section.
The compressor section raises the pressure of the air it receives from the fan section to a relatively high level. In a multi-spool engine, the compressor section may include two or more compressors, such as, for example, a high pressure compressor and a low pressure compressor. The compressed air from the compressor section then enters the combustor section, where a ring of fuel nozzles injects a steady stream of fuel into a plenum formed by liner walls and a dome. The injected fuel is ignited in the combustor, which significantly increases the energy of the compressed air. The high-energy compressed air from the combustor section then flows into and through the turbine section, causing rotationally mounted turbine blades to rotate and generate energy. The air exiting the turbine section is exhausted from the engine via the exhaust section, and the energy remaining in the exhaust air aids the thrust generated by the air flowing through the bypass plenum.
During engine operation, vibration may occur when the rotor and components mounted thereto rotates. Typically, the vibration is caused by a rotating mass imbalance, or may occur when a radial deflection of the rotor results in tangential force normal to the deflection. The magnitude of the tangential force increases with the deflection. A damping system is typically needed in the engine to reduce vibration, there by, minimizing fatigue stress on the engine and its supports, and to safeguard against potential damage that can be caused by vibration.
In some cases, a squeeze film damper is included in the engine. Typically, the squeeze film damper operates by supplying fluid (usually oil) through dedicated oil delivery passages into a cavity between the engine housing and a bearing support mounted around the rotor. Although this configuration is useful for bearing locations in the aft sections of the engine, it may be as useful in the forward sections of the engine, more particularly, those locations that are exposed to temperatures in excess of 700° F. Specifically, because the aft sections of the engine, such as the combustor section and the turbine section, reaches such high temperatures, the fluid therein may solidify or cause coking of other components. Consequently, debris build-up in the oil delivery passages may occur restricting oil flow and causing damage thereto.
Thus, there is a need for an engine damping system that remains operational when exposed to temperatures in excess of 500° F. Moreover, it is desirable for the system not to create debris build-up that may damage the engine. Additionally, it is desirable for the system to be relatively simple and inexpensive to implement.